The slides and movies in the presentation are updated automatically for remote users. Open the presentation in progress page on one or more systems first, then control the presentation.
The web and QuickTime interfaces for controlling the presentation are normally protected by an Apache realm. Each user on a server would have their own private instances of one or more presentation directories. For this demonstration site you can control and organize the presentation without a password. If more than one person controls the presentation simultaneously - it's a free for all.